U.S. patent number 4,098,351 [Application Number 05/820,284] was granted by the patent office on 1978-07-04 for hammer tool.
This patent grant is currently assigned to The Black and Decker Manufacturing Company. Invention is credited to Lorenzo Ercole Alessio.
United States Patent |
4,098,351 |
Alessio |
July 4, 1978 |
Hammer tool
Abstract
A hammer tool such as a rotary hammer, hammer drill or the like
includes a motor housing and a gear case secured to the motor
housing forwardly of the motor housing. A motor in the motor
housing has a shaft projecting into the gear case and a pinion
formed on the end of the motor shaft. A first set of ratcheting
teeth is formed on a body rotatably journaled in the gear case. An
output spindle for holding a tool bit is provided and has a
longitudinal axis. The output spindle is rotatably journalled in
the gear case so as to be also slideable in the direction of said
longitudinal axis. A second set of ratcheting teeth is mounted on
the output spindle so as to be in confronting relation to the first
set of ratcheting teeth. A spring provides a resilient force for
holding the first and second sets of ratcheting teeth in spaced
apart relation to each other. A gear transmission is operatively
connected to the pinion for simultaneously rotating the first set
of ratcheting teeth at a predetermined first angular velocity and
for rotating the second set of ratcheting teeth at a predetermined
second angular velocity whereby one of the sets of ratcheting teeth
ratchets over the other one of the sets of ratcheting teeth thereby
imparting longitudinal impact blows to the output spindle when the
first set of ratcheting teeth and the second set of ratcheting
teeth mutually engage in response to an axial movement of the
output spindle caused by the tool being pressed toward a work
surface against the resilient force developed by the spring.
Inventors: |
Alessio; Lorenzo Ercole (Lecco,
IT) |
Assignee: |
The Black and Decker Manufacturing
Company (Towson, MD)
|
Family
ID: |
11218767 |
Appl.
No.: |
05/820,284 |
Filed: |
July 29, 1977 |
Foreign Application Priority Data
|
|
|
|
|
Aug 9, 1976 [IT] |
|
|
26154 A/76 |
|
Current U.S.
Class: |
173/13; 173/104;
173/48; 74/56 |
Current CPC
Class: |
B25D
11/005 (20130101); B25D 16/00 (20130101); B25D
2211/064 (20130101); Y10T 74/18304 (20150115) |
Current International
Class: |
B25D
16/00 (20060101); B25D 11/00 (20060101); B23Q
005/027 () |
Field of
Search: |
;173/13,48,104,109,47
;74/56,57 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hafer; Robert A.
Attorney, Agent or Firm: Ottesen; Walter Bloom; Leonard
Murphy; Edward D.
Claims
I claim:
1. A portable hammer tool such as a rotary hammer, hammer drill or
the like comprising:
a motor housing;
a gear case secured to said motor housing forwardly of said motor
housing;
a motor in said motor housing having a shaft projecting into said
gear case;
a pinion formed on the end of said motor shaft;
first ratcheting means rotatably journaled in said gear case;
an output spindle for holding a tool bit, said output spindle
having a longitudinal axis and being rotatably journalled in said
gear case so as to be also slideable in the direction of said
longitudinal axis;
second ratcheting means fixedly mounted to said output spindle so
as to be in confronting relation to said first ratchet means;
resilient means providing a resilient force for holding said first
and said second ratcheting means in spaced apart relation to each
other; and,
gear transmission means operatively connected to said pinion for
simultaneously rotating said first ratcheting means at a
predetermined first angular velocity and for rotating said second
ratcheting means at a predetermined second angular velocity whereby
one of said ratcheting means ratchets over the other one of said
ratcheting means thereby imparting longitudinal impact blows to
said output spindle when said first ratcheting means and said
second ratcheting means mutually engage in response to an axial
movement of said output spindle caused by the tool being pressed
toward a work surface against the resilient force developed by said
resilient means.
2. The portable hammer tool of claim 1, wherein the difference
between said first predetermined angular velocity and said second
predetermined angular velocity is the differential angular
velocity, said gear transmission means including gear means for
causing said differential angular velocity to have a value which
will cause the impact blows per revolution of said output spindle
to be a non-integer number.
3. The portable hammer tool of claim 2, said non-integer number
being greater than 1.
4. The portable hammer tool of claim 1, said gear transmission
means including gear means for causing said predetermined first
angular velocity to be greater than said predetermined second
angular velocity.
5. The portable hammer tool of claim 4, wherein the difference
between said first predetermined angular velocity and said second
predetermined angular velocity is the differential angular
velocity, said gear transmission means further including means for
causing said differential angular velocity to have a value which
will cause the impact blows per revolution of said output spindle
to be a non-integer number.
6. The portable hammer tool of claim 5, said non-integer number
being greater than 1.
7. A portable hammer tool such as a rotary-hammer, hammer-drill or
the like comprising:
a motor housing;
a gear case cover secured to said motor housing;
a gear case secured to said motor housing forwardly of said gear
case cover;
a motor in said motor housing having a shaft journaled in said gear
case cover and projecting within said gear case;
a pinion formed on the end of said motor shaft;
an output spindle for holding a tool bit, said output spindle
having a longitudinal axis and being rotatably journaled in said
gear case so as to be also slideable in the direction of said
longitudinal axis;
first ratcheting means mounted on said output spindle so as to be
rotatable with respect thereto;
second ratcheting means fixedly mounted on said output spindle
axially of said first ratcheting means so as to be in confronting
relation to the latter;
resilient means for resiliently holding said first and second
ratcheting means in spaced apart relation to each other; and,
gear transmission means operatively connected to said pinion for
simultaneously rotating said first ratcheting means at a
predetermined first angular velocity and for rotating said second
ratcheting means at a predetermined second angular velocity whereby
one of said ratcheting means ratchets over the other one of said
ratcheting means thereby imparting longitudinal impact blows to
said output spindle when said first ratcheting means and said
second ratcheting means mutually engage in response to an axial
movement of said output spindle caused by the tool being pressed
toward a work surface against the resilient force developed by said
resilient means.
8. The portable hammer tool of claim 7 wherein the difference
between said first predetermined angular velocity and said second
predetermined angular velocity is the differential angular
velocity, said gear transmission means including gear means for
causing said differential angular velocity to have a value which
will cause the impact blows per revolution of said output spindle
to be a non-integer number.
9. The portable hammer tool of claim 8, said non-integer being
greater than 1.
10. The portable hammer tool of claim 7, said gear transmission
means including gear means for causing said predetermined first
angular velocity to be greater than said predetermined second
angular velocity.
11. The portable hammer tool of claim 10, wherein the difference
between said first predetermined angular velocity and said second
predetermined angular velocity is the differential angular
velocity, said gear transmission means further including means for
causing said differential angular velocity to have a value which
will cause the impact blows per revolution of said output spindle
to be a non-integer number.
12. The portable hammer tool of claim 11, said non-integer number
being greater than 1.
13. A portable hammer tool such as a rotary hammer, hammer drill or
the like comprising:
a motor housing;
a gear case cover secured to said motor housing;
a gear case secured to said motor housing forwardly of said gear
case cover;
a motor in said motor housing having a shaft journaled in said gear
case cover and projecting within said gear case;
an output spindle for holding a tool bit, said output spindle
having a longitudinal axis and rotatably journaled in said gear
case so as to be also slideable in the direction of said
longitudinal axis;
a gear body having at least two gears formed thereon and mounted on
said output spindle so as to be rotatable with respect thereto;
a pinion formed on the end of said motor shaft and engaging a first
one of said two gears on said gear body;
a third gear fixedly disposed on said output spindle so as to be
rotatable therewith;
an intermediate shaft journaled in said gear case on an axis
parallel to, and radially offset from, said output spindle;
a pair of spaced-apart gears of predetermined size carried by said
intermediate shaft, one of said gears of said pair being in mesh
with the second one of said two gears of said gear body and the
other one of said gears of said pair being in mesh with said third
gear;
first ratcheting means formed on one end-face of said gear
body;
second ratcheting means fixedly disposed on said output spindle
axially of said first ratcheting means so as to be in confronting
relation to the latter;
resilient means for resiliently holding said first and second
ratcheting means in spaced apart relation to each other; and,
each of said gears being dimensioned so as to cause said gear body
to rotate at an angular velocity faster than said output spindle
thereby causing said first ratcheting means to ratchet over said
second ratcheting means thereby imparting longitudinal impact blows
to said output spindle when said first ratcheting means and said
second ratcheting means mutually engage in response to an axial
movement of said output spindle caused by the tool being pressed
toward a work surface against the resilient force developed by said
resilient means.
14. A portable hammer tool such as a rotary-hammer, hammer-drill or
the like comprising:
a motor housing;
a gear case secured to said motor housing forwardly of said gear
case cover;
a motor in said motor housing having a shaft projecting into said
gear case;
a body of predetermined mass rotatably journaled in said gear
case;
first ratcheting means formed on said body;
an output spindle for holding a tool bit, said output spindle
having a longitudinal axis and being rotatably journaled in said
gear case so as to be also slideable in the direction of said
longitudinal axis;
second ratcheting means mounted on said output spindle axially of
said first ratcheting means so as to be in confronting relation to
the latter;
resilient means for resiliently holding said first and second
ratcheting means in spaced apart relation to each other;
first kinematic means for kinematically connecting said body to
said motor shaft and for rotating said body and said first
ratcheting means at a predetermined first angular velocity;
and,
second kinematic means for kinematically connecting said output
spindle to said motor shaft and for rotating said output spindle at
a predetermined second angular velocity whereby one of said
ratcheting means ratchets over the other one of said ratcheting
means thereby imparting longitudinal impact blows to said output
spindle when said first ratcheting means and said second ratcheting
means mutually engage in response to an axial movement of said
output spindle caused by the tool being pressed toward a work
surface against the resilient force developed by said resilient
means.
15. The portable tool of claim 14, said first kinematic means and
said second kinematic means being a gear transmission having gear
ratios selected to cause said predetermined first angular velocity
to be greater than said predetermined second angular velocity.
16. The portable tool of claim 15 wherein the difference between
said first predetermined angular velocity and said second
predetermined angular velocity is the differential angular
velocity, said gear ratios being further selected to cause said
differential angular velocity to have a value which will cause the
impact blows per revolution of said output spindle to be a
non-integer number.
17. The portable tool of claim 14, said first kinematic means
comprising:
a pinion formed on the end of said shaft projecting into said gear
case; and,
a first gear formed on said body and meshing with said pinion.
18. The portable tool of claim 17, said second kinematic means
comprising:
said first kinematic means;
a second gear formed on said body;
a third gear fixedly disposed on said output spindle so as to be
rotatable therewith;
an intermediate shaft journaled in said gear case on an axis
parallel to, and radially offset from, said output spindle;
and,
a pair of spaced-apart gears of predetermined size carried by said
intermediate shaft, one of said gears of said pair being in mesh
with the second one of said two gears of said gear body and the
other one of said gears of said pair being in mesh with said third
gear.
19. The portable tool of claim 18, the gear ratio of said first
kinematic means and the gear ratios of said second kinematic means
being selected to cause said predetermined first angular velocity
to be greater than said predetermined second angular velocity.
20. The portable tool of claim 19, wherein the difference between
said first predetermined angular velocity and said second
predetermined angular velocity is the differential angular
velocity, said gear ratios being further selected to cause said
differential angular velocity to have a value which will cause the
impact blows per revolution of said output spindle to be a
non-integer number.
21. A portable hammer tool such as a rotary hammer, hammer drill or
the like comprising:
a motor housing;
a gear case secured to said motor housing forwardly of said motor
housing;
a motor in said motor housing having a shaft projecting into said
gear case;
a pinion formed on the end of said motor shaft;
first ratcheting means rotatably journaled in said gear case;
an output spindle for holding a tool bit, said output spindle
having a longitudinal axis and being rotatably journalled in said
gear case so as to be also slideable in the direction of said
longitudinal axis;
second ratcheting means mounted on said output spindle so as to be
in confronting relation to said first ratchet means;
resilient means providing a resilient force for holding said first
and said second ratcheting means in spaced apart relation to each
other; and,
gear transmission means operatively connected to said pinion for
simultaneously rotating said first ratcheting means at a
predetermined first angular velocity and for rotating said second
ratcheting means at a predetermined second angular velocity whereby
one of said ratcheting means ratchets over the other one of said
ratcheting means thereby imparting longitudinal impact blows to
said output spindle when said first ratcheting means and said
second ratcheting means mutually engage in response to an axial
movement of said output spindle caused by the tool being pressed
toward a work surface against the resilient force developed by said
resilient means, said gear transmission means also including means
for rotating said output spindle at a predetermined third angular
velocity.
22. The portable hammer tool of claim 1, wherein the difference
between said first predetermined angular velocity and said second
predetermined angular velocity is the differential angular
velocity, said gear transmission means including gear means for
causing said differential angular velocity to have a value which
will cause the impact blows per revolution of said output spindle
to be a non-integer number.
23. The portable hammer tool of claim 22, said non-integer member
being greater than 1.
24. The portable hammer tool of claim 21, said gear transmission
means including gear means for causing said predetermined first
angular velocity to be greater than said predetermined second
angular velocity.
25. The portable hammer tool of claim 24, wherein the difference
between said first predetermined angular velocity and said second
predetermined angular velocity is the differential angular
velocity, said gear transmission means further including means for
causing said differential angular velocity to have a value which
will cause the impact blows per revolution of said output spindle
to be a non-integer number.
26. The portable hammer tool of claim 25, said non-integer number
being greater than 1.
27. The portable hammer tool of claim 24 wherein the difference
between said predetermined first angular velocity and said
predetermined second angular velocity is the differential angular
velocity, and wherein said gear transmission means includes speed
changing means for changing said differential angular velocity.
28. The portable hammer tool of claim 27, said gear transmission
means further including means for causing said differential angular
velocity to have a value which will cause the impact blows per
revolution of said output spindle to be a non-integer number.
29. The portable hammer tool of claim 28, said non-integer number
being greater than 1.
30. A portable hammer tool such as a rotary-hammer, hammer-drill or
the like comprising:
a motor housing;
a gear case cover secured to said motor housing;
a gear case secured to said motor housing forwardly of said gear
case cover;
a motor in said motor housing having a shaft journaled in said gear
case cover and projecting within said gear case;
a pinion formed on the end of said motor shaft;
an output spindle for holding a tool bit, said output spindle
having a longitudinal axis and being rotatably journaled in said
gear case so as to be also slideable in the direction of said
longitudinal axis;
first ratcheting means mounted on said output spindle so as to be
rotatable with respect thereto;
second ratcheting means also mounted on said output spindle so as
to be rotatable with respect thereto, said second ratcheting means
being disposed axially of said first ratcheting means so as to be
in confronting relation to the latter;
said output spindle including means for restraining the movement of
said second ratcheting means in at least one direction along said
longitudinal axis;
resilient means for resiliently holding said first and second
ratcheting means in spaced apart relation to each other; and,
gear transmission means operatively connected to said pinion for
simultaneously rotating said first ratcheting means at a
predetermined first angular velocity and for rotating said second
ratcheting means at a predetermined second angular velocity whereby
one of said ratcheting means ratchets over the other one of said
ratcheting means thereby imparting longitudinal impact blows to
said output spindle when said first ratcheting means and said
second ratcheting means mutually engage in response to an axial
movement of said output spindle caused by the tool being pressed
toward a work surface against the resilient force developed by said
resilient means, said gear transmission means also including means
for rotating said output spindle at a predetermined third angular
velocity.
31. The portable hammer tool of claim 30 wherein the difference
between said first predetermined angular velocity and said second
predetermined angular velocity is the differential angular
velocity, said gear transmission means including gear means for
causing said differential angular velocity to have a value which
will cause the impact blows per revolution of said output spindle
to be a non-integer number.
32. The portable hammer tool of claim 31, said non-integer being
greater than 1.
33. The portable hammer tool of claim 30, said gear transmission
means including gear means for causing said predetermined first
angular velocity to be greater than said predetermined second
angular velocity.
34. The portable hammer tool of claim 33, wherein the difference
between said first predetermined angular velocity and said second
predetermined angular velocity is the differential angular
velocity, said gear transmission means further including means for
causing said differential angular velocity to have a value which
will cause the impact blows per revolution of said output spindle
to be a non-integer number.
35. The portable hammer tool of claim 34, said non-integer number
being greater than 1.
36. A portable hammer tool such as a rotary hammer, hammer drill or
the like comprising:
a motor housing;
a gear case secured to said motor housing forwardly of said gear
case cover;
a motor in said motor housing having a shaft projecting into said
gear case;
a pinion formed on the end of said motor shaft;
first ratcheting means rotatably journaled in said gear case;
an output spindle for holding a tool bit, said output spindle
having a longitudinal axis and being rotatably journalled in said
gear case so as to be also slideable in the direction of said
longitudinal axis;
second ratcheting means mounted to said output spindle so as to be
in confronting relation to said first ratchet means;
resilient means providing a resilient force for holding said first
and said second ratcheting means in spaced apart relation to each
other;
gear transmission means operatively connected to said pinion for
simultaneously rotating said first ratcheting means at a
predetermined first angular velocity and for rotating said second
ratcheting means at a predetermined second angular velocity whereby
one of said ratcheting means ratchets over the other one of said
ratcheting means thereby imparting longitudinal impact blows to
said output spindle when said first ratcheting means and said
second ratcheting means mutually engage in response to an axial
movement of said output spindle caused by the tool being pressed
toward a work surface against the resilient force developed by said
resilient means, the difference between said predetermined first
angular velocity and said predetermined second angular velocity
being the differential angular velocity; and,
said gear transmission means including speed changing means for
changing said differential angular velocity.
37. The portable hammer tool of claim 36, said gear transmission
means further including means for causing said differential angular
velocity to have a value which will cause the impact blows per
revolution of said output spindle to be a non-integer number.
38. The portable hammer tool of claim 37, said non-integer number
being greater than 1.
39. The portable hammer tool of claim 36, said gear transmission
means including gear means for causing said predetermined first
angular velocity to be greater than said predetermined second
angular velocity.
40. The portable hammer tool of claim 39, said gear transmission
means further including means for causing said differential angular
velocity to have a value which will cause the impact blows per
revolution of said output spindle to be a non-integer number.
41. The portable hammer tool of claim 40, said non-integer number
being greater than 1.
42. In a hammer tool equipped with a motor housing, a gear case
secured to the motor housing, a motor in the motor housing having a
shaft projecting into the gear case, the shaft having a pinion
formed on the end thereof projecting into the gear case, an output
spindle for holding a tool bit, said output spindle having a
longitudinal axis and being rotatably journaled in said gear case
so as to be also slideable in the direction of said longitudinal
axis, and wherein the improvement comprises a ratcheting
arrangement including:
first ratcheting means rotatably journaled in said gear case;
second ratcheting means mounted on said output spindle axially of
said first ratcheting means so as to be in confronting relation to
the latter;
resilient means for resiliently holding said first and second
ratcheting means in spaced apart relation to each other; and,
gear transmission means operatively connected to said pinion for
simultaneously rotating said first ratcheting means at a
predetermined first angular velocity and for rotating said second
ratcheting means at a predetermined second angular velocity whereby
one of said ratcheting means ratchets over the other one of said
ratcheting means thereby imparting longitudinal impact blows to
said output spindle when said first ratcheting means and said
second ratcheting means mutually engage in response to an axial
movement of said output spindle caused by the tool being pressed
toward a work surface against the resilient force developed by said
resilient means.
43. The hammer tool of claim 42, wherein the difference between
said first predetermined angular velocity and said second
predetermined angular velocity is the differential angular
velocity, said gear transmission means including gear means for
causing said differential angular velocity to have a value which
will cause the impact blows per revolution of said output spindle
to be a non-integer number.
44. The hammer tool of claim 43, said non-integer member being
greater than 1.
45. The hammer tool of claim 42, said gear transmission means
including gear means for causing said predetermined first angular
velocity to be greater than said predetermined second angular
velocity.
46. The hammer tool of claim 45, wherein the difference between
said first predetermined angular velocity and said second
predetermined angular velocity is the differential angular
velocity, said gear transmission means further including means for
causing said differential angular velocity to have a value which
will cause the impact blows per revolution of said output spindle
to be a non-integer number.
47. The hammer tool of claim 46, said non-integer number being
greater than 1.
48. The hammer tool of claim 45, wherein the difference between
said first predetermined angular velocity and said second
predetermined angular velocity is the differential angular
velocity, said gear transmission means including speed changing
means for changing said differential angular velocity.
49. The hammer tool of claim 48, said gear transmission means
including gear means for causing said differential angular velocity
to have a value which will cause the impact blows per revolution of
said output spindle to be a non-integer number.
50. The portable hammer tool of claim 49, said non-integer being
greater than 1.
51. The hammer tool of claim 45 comprising a body of predetermined
mass rotatably journaled in said gear case, said first ratcheting
means being formed on said body.
Description
BACKGROUND OF THE INVENTION
Drills, generally of the portable type, are known wherein the
output spindle on which the chuck is mounted performs a rotary
movement as well as an axial reciprocating movement. The percussion
effect resulting from such an axial reciprocating movement provides
advantages when perforating materials having a tendency to crumble
as opposed to materials which can be drilled by conventional
methods involving the removal of chips in the course of the cutting
action. Concrete stone, and the like are materials which tend to
crumble.
As a rule, the axial reciprocating movement is brought about
through the interaction of two sets of ratchet teeth shaped in the
form of a cam, with one element being integral with the stationary
portion of the drill while the other one is integral with the
output spindle shaft. The axial pressure that is exerted by the
operator onto the bit during the drilling operation causes the
output spindle to bring the movable set of rachet teeth in contact
with the stationary set of ratchet teeth. The overlapping of the
respective sets of teeth of suitable profile results in a
successive moving away of the output spindle shaft and the set of
ratchet teeth mounted thereon. The respective sets of teeth are
caused to reestablish contact through the pressure exerted by the
operator on the drill so that the successive engagements of the
teeth sets produces a beating action that is causing, in turn, the
percussion of the output spindle and the chuck and tool bit mounted
on the output spindle.
Such a mode of operation presupposes that the entire body of the
drill constitutes the inertial reaction mass of the percussion
effort of the output spindle, chuck and tool bit.
The shape of the stationary and movable ratchet teeth can generally
be that of a sawtooth profile in which the inclined sections
constitute the impact surfaces. The result is that the reaction on
the stationary gear is not axial but has, on the contrary, an axial
component and a tangential component on the plane perpendicular to
the axis of the output spindle. Both of these components are
rigidly transmitted to the body of the conventional
hammer-drill.
It ought to be pointed out likewise that the above-mentioned
conventional configuration of the percussion drill takes into
account as a necessary consequence that the number of percussions
per revolution of the output spindle be defined solely by the
number of teeth of the stationary set of ratchet teeth and the
rotating set of ratchet teeth. It follows from this premise that
the percussion frequency is a linear function of direct
proportionality to the speed of rotation of the output spindle
which may not be desirable in all instances. Moreover, another
inevitable consequence is that each percussion or impact blow may
be in a well-defined angular position of the output spindle shaft;
whereas, it would be advantageous to have a continuous variability
so as to attack, in changing positions, the material subjected to
the percussion force. By continously varying the angular positions
at which the bit strikes the workpiece, such as concrete for
example, a round bore is obtained rather than one which takes on
the general contour of bit. This prevents the bit from binding in
the workpiece.
SUMMARY OF THE INVENTION
It is an object of my invention to provide a hammer tool wherein
the frequency of the impact blows received by the output spindle
can be selected by appropriate design of the gear transmission
arrangement. Subsidiary to this object, it is another object of my
invention to provide a hammer tool wherein this frequency can be
selected independently of the speed of the output spindle.
It is another object of the invention to provide a hammer tool
wherein the angular position of the shaft in which the percussions
occur is varied with each revolution of the output spindle.
Moreover, it is an object of the invention to make it possible to
reduce the intensity of vibration of the housing of the hammer tool
during the percussion, thereby making the tool more comfortable to
operate and reducing the hazards to which the components making up
the tool are subjected.
The hammer tool of the invention can be a rotary hammer,
hammer-drill or the like. Hammer tools of this type are equipped
with an output spindle for holding a tool bit. The output spindle
has a longitudinal axis and is rotatably journaled in the gear case
of the tool so as to be also slideable in the direction of the
longitudinal axis.
According to a feature of the invention, a first set of ratchet
teeth are formed on a body also rotatably journalled in the gear
case. A second set of ratchet teeth are mounted on the output
spindle for transmitting impact blows thereto when the two sets of
ratchet teeth come together. The two sets of ratchet teeth are in
confronting relation to each other. Resilient means such as a
spring holds the first and second sets of ratchet teeth in spaced
apart relation to each other.
Another feature of the invention is a gear transmission operatively
connected to the pinion of the motor of the tool for simultaneously
rotating the first set of ratchet teeth at a predetermined first
angular velocity and for rotating the second set of ratchet teeth
at a predetermined second angular velocity whereby one of the sets
of ratchet teeth ratchets over the other one of the sets of ratchet
teeth thereby imparting longitudinal impact blows to the output
spindle when the first set of ratchet teeth and the second set of
ratchet teeth mutually engage in response to an axial movement of
the output spindle caused by the tool being pressed toward a work
surface against the resilient force developed by the resilient
means.
The difference between the first predetermined angular velocity and
the second predetermined angular velocity is the differential
angular velocity. According to another feature of the invention the
gear transmission means including gear means for causing the
differential angular velocity to have a value which will cause the
impact blows per revolution of the output spindle to be a
non-integer number. Preferably, the non-integer number is greater
than 1.
Still another feature of the invention is that the gear
transmission means includes gear means for causing the
predetermined first angular velocity to be greater than the
predetermined second angular velocity.
BRIEF DESCRIPTION OF THE DRAWING
The foregoing objects and advantages of my invention will become
more apparent from consideration of the detailed description to
follow taken in conjunction with the drawing annexed hereto
wherein;
FIG. 1 is an elevation view of a hammer-drill according to the
invention;
FIG. 2 is an elevation view, partially in section, showing the gear
case of a single-speed hammer-drill containing a reduction gear
arrangement connected to the motor shaft for rotating the ratchet
teeth sets at predetermined angular velocities;
FIG. 3 is an assembly view of the gear reduction arrangement of
FIG. 2;
FIG. 4 is an elevation view, partially in section showing the gear
case of a single-speed hammer-drill containing a simplified
reduction gear arrangement requiring less gears than the embodiment
shown in FIGS. 2 and 3;
FIG. 5 is an elevation view, partially in section, showing the gear
case of a two-speed hammer-drill containing a reduction gear
arrangement connected to the motor shaft for rotating the ratchet
teeth sets at predetermined angular velocities;
FIG. 6 shows the two-speed hammer-drill of FIG. 6 wherein a gear
body has been shifted to cause the hammer-drill to be operable at a
different speed;
FIG. 7 illustrates a single-speed hammer-drill equipped with a gear
transmission arrangement that rotates the output spindle shaft at a
different angular velocity than either one of the sets of
ratcheting teeth;
FIG. 8 is a section view taken along line 8--8 of FIG. 2; and,
FIG. 9 illustrates a helical gear configuration for the motor
pinion and the gear with which the pinion engages.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
FIG. 1 illustrates a hammer-drill according to the invention
designated by reference numeral 1 and having a gear case 10 and a
drive motor 2 contained within a motor housing 3.
FIG. 2 illustrates the gear case of the hammer-drill of FIG. 1 and
is again designated by reference numeral 10. The shaft 11 of the
rotor of the drive motor extends into the gear case 10. Gears 13
and 14 are formed on a unitary gear body 8 which is mounted on
shaft 19 so as to be rotatable with respect thereto. A pinion 12 is
formed on the end of the shaft 11 to engage with the gear 13 to
rotate the gear 13 and gear body 8 on shaft 19. The second gear 14,
in turn, engages gear 15. Gear 15 and gear 17 are coaxial and
conjointly define a gear body 5 which is fixedly mounted on
intermediate shaft 16 so as to be rotatable therewith. The shaft 16
is rotatably journaled in bearing 4 in gear case 10 and a bearing
(not shown) in the gear-case cover 9. The gear 17 engages gear 18
integrally connected to the shaft 19. A chuck 30 threadably engages
a threaded front-end extension 31 of shaft 19. The shaft 19 is
rotatably supported in bearings 20 and 6 and constitutes the output
spindle. The shaft 19 is further held in bearings 20 and 6 so as to
be axially slideable therein in the direction of the longitudinal
axis of the shaft. An axial thrust is exerted upon the shaft 19 by
a spring 21 which is compressed between the gear case 10 and a
cup-shaped collar 22 mounted on the shaft proper. Cup-shaped piece
46 contains a thrust bearing 47 and flat washers 48 and 49.
Reference numerals 50 and 51 indicate a Belleville spring and a
flat washer, respectively.
Another spring 23 is compressed between gear body 8 and gear body 7
on which gear 18 is formed. If indeed it is desired to use the
drill for the purpose of drilling operations without percussion
motion, it is known in the art to provide means to block the axial
movement of the chuck shaft 19 subjected to the drilling pressure.
Under such conditions and especially if the drill is held in
vertical position, the gear body 8 can descend of its own weight so
as to cause ratchet teeth 24 and 25 to mutually engage producing
noise. The spring 23 eliminates such a disadvantage. This
disadvantage could, however, be obviated in other ways, for
example, by designing the gear 13 with a helical gear engaging the
pinion 12 that is inclined in a direction to generate on the gear
body 8 at gear 13 an axial thrust that moves the same away from the
wheel 18. Such an arrangement is shown in FIG. 9 wherein a helical
gear 13A on the body 8 is engaged by a corresponding helical pinion
gear 12A.
A perspective assembly view of the reduction gear arrangement of
FIG. 2 is shown in FIG. 3. The gear reduction arrangement is
configured so that the gear 13 rotates faster than the gear 18.
Collar 44 (not shown in FIG. 2) coacts with recesses 45 formed in
the gear-case cover 10 as explained in Italian patent application
No. 24323 A/75 filed on June 12, 1975 as well as in Italian Utility
Model Application No. 21671 B/75 likewise filed on June 12,
1975.
A set of ratchet teeth 24 are formed on the front end-face of gear
body 8 and are dimensioned so as to engage with a corresponding
second ratcheting means in the form of a set of ratchet teeth 25
formed on the back end-face of gear 18. The ratchet teeth 24 and 25
are preferably beveled so as to mutually overlap when the bear body
8 and the body 7 of gear 18 are forced toward one another while
rotating at different angular velocities. Suitable are for instance
teeth 24 having a sawtooth configuration as shown in FIG. 3 which
take into account the fact that gear 13 rotates faster than the
gear 18 and, therefore, that the teeth 24 rotate faster than the
teeth 25.
The spring 21 constitutes resilient means and develops a resilient
force between the gear case 10 and the spindle shaft 19 to
resiliently hold the ratchet teeth sets 24 and 25 in spaced apart
relation to each other. As mentioned, a spring 23 can also be added
if desired to prevent the gear body 8 from falling down upon the
gear body 7 of gear 18 when the tool is in the vertical
position.
Generally, it should be pointed out that the end-face teeth
indicated by reference numerals 24 and 25 are of cam-like
configuration so that when these teeth mutually engage, a
ratcheting effect is achieved which causes the shaft 19 to
reciprocate when the hammer-drill is placed under load by the
operator of the tool. When the operator presses the tool toward a
work surface he overcomes the resilient force developed by the
resilient means 21 and the teeth sets 24 and 25 to ratchet. The
operator must also overcome the resilient force of spring 23 if it
should be present in which case it too can be considered as being
part of the resilient means.
The rotational movement is imparted to the shaft 19 through three
pairs of cascade-type reduction gears, namely: the gear parts
12-13, 14-15, and 17-18. FIG. 8 is a section view taken along line
8--8 of FIG. 2 and shows the disposition of these gears.
At the instant an axial force acts upon the chuck 30, the entire
shaft 19 will slide toward the right. The body 7 of gear 18 bears
with its teeth 25 on the teeth 24 of the gear body 8 thereby
initiating a percussion effect each time teeth 25 overlap the teeth
24 as they rotate at different angular velocities. When the axial
force is interrupted, as for example when the hammer-drill is
lifted off of the workpiece, the spring 21 and spring 23 act to
move the ratchet teeth sets 24 and 25 apart as shown in FIG. 2.
The relative angular velocity between the teeth 24 and 25 differs
from the absolute angular velocity of the shaft 19 of the chuck and
is governed by the reduction gear pairs 14-15 and 17-18. The
percussion frequency is a function of the number of teeth and the
relative angular velocity between the teeth 25 and the teeth 24.
More specifically and assuming that gear bodies 7 and 8 both have
the same number of teeth t the number of strokes n per minute is
given by the equation:
where w.sub.a and w.sub.b are the angular velocities of gear bodies
8 and 7, respectively. w.sub.d is the relative or differential
angular velocity.
By appropriately configuring the speed reduction gears, the most
suitable percussion frequency can be achieved and maximum freedom
for the design of the teeth 24 and 25 is achieved. Thus, these
teeth can be provided with an optimum tooth configuration with
respect to tooth height, flank inclination and, accordingly, the
number of teeth.
According to a preferred embodiment of my invention, the gear
reduction arrangement is designed to provide a differential angular
velocity w.sub.d which will cause the number of impact blows per
revolution of the output spindle shaft 19 to be a non-integer
member. Preferably, the number of blows per revolution of the
output shaft is an integral number plus a fraction. In this way,
the angular position of the shaft 19 of the chuck 30 at which a
percussion impluse is received is varied continuously so that the
bore hammer-drilled by the tool into a workpiece such as concrete
is a clean round bore.
The particular dynamic equilibrium generated by the structure of
the invention should be noted. The reaction force generated by the
teeth 24-25 is transmitted to the gear body 8 rather than directly
to the hammer-drill housing.
The placement of gear body 8 between the gear 18 and the gear case
10 affords special advantages because the gear body 8 has a mass
having its own inertia and revolving at considerable angular speed.
It has been shown that this arrangement according to the invention
substantially attenuates the vibrations that, in conventional
drills, affect the housing as a whole and do therefore transmit
vibrations to the handle and thereby to the operator. Attention is
called to the fact that in a conventional hammer-drill, one set of
teeth are fixedly connected to the gear case and the vibration of
the ratcheting teeth are transmitted directly to the operator when
the tool is operated in the hammer mode.
The greater the mass of the gear body 8, the more efficient will be
the system because more rotational energy is stored between blows.
The gear reduction arrangement shown in FIG. 2 is preferably
designed so that gear body 8 rotates in the same angular direction
as the gear body 7 on the output shaft 19. In addition, the gear
body 8 and teeth 24 rotate at a greater angular velocity then the
gear body 7 and teeth 25 so that the rotating spindle shaft 19
receives an assist in its rotation into the workpiece as a
consequence of the teeth 24 ratcheting over the teeth 25.
The tangential component of the force exerted on the ratchet teeth
24 is taken up by the engagement of the driving pinion 12 with the
gear 13. The ratchet teeth 24 can be seen in the assembly view of
FIG. 3.
It is possible that a different kinematic chain be utilized to
connect the driving pinion 12 to the output spindle 19 without
affecting the rotary mass borne by the reaction gear body 8 which
can be independently driven by taking its rotary movement from any
motor-to-output spindle transmission drive.
By way of example, FIG. 4 illustrates another embodiment
incorporating the principle referred to above wherein the pinion 12
engages directly with the gear 15 which, in turn, meshes with the
gear 14 on which there has been machined the front ratchet teeth
24. This eliminates the gear 13 of the embodiment of FIG. 2. In
this way, the ratchet teeth 24 are driven by a transmission
12-15-14, and the output spindle 19 by a transmission
12-15-17-18.
FIG. 5 illustrates a reduction gear arrangement equipped with
alternate gear ratios. In this embodiment, the intermediate shaft
16 includes gears 17 and 27. The gear 18 is integral with a gear 28
and the assembly is slidably mounted on the shaft 19 whereas the
gear body 32 of gears 18 and 28 is constrained to rotate with the
shaft 19.
A control lug 29 is capable of moving the gear body 32 from the
position shown in FIG. 5 to the position illustrated in FIG. 6 for
the purpose of respectively connecting the gear 17-18 and the gears
27-28. In this way, it is possible to change the speed of the
output spindle 19. The ratcheting means 25 is separately attached
to the output spindle 19.
It can be noted that, with such an arrangement, the frequency of
the percussions decreases with the increase in the speed of the
output spindle 19, which is slower than the gear 13 and gear body 8
upon which ratcheting means 24 are formed. This effect may not be
unwelcome in view of the fact that the drilling of relatively soft
material in which the tool can operate at higher speed does not
necessarily call for a very high percussion frequency. Thus,
according to a further feature of the invention speed changing
means can be provided for changing the differential angular
velocity thereby causing the number of impact blows per revolution
of the output spindle 19 imparted to the output spindle 19 to be
changed.
As stated above, the gearing for the reduction of the revolutions
between the drive shaft 11 and the output spindle 19 can have any
other configuration, and the ratcheting arrangement for imparting
impacting blows to the output spindle 19 can likewise be of a
different configuration.
According to still another embodiment of the invention, at least
one of the gear bodies on which a set of ratcheting teeth are
formed is mounted on the output spindle shaft 19 so as not be be
integral therewith, it being adequate if this gear body is mounted
to transmit precisely the axial percussion pressure applied to the
output spindle 19. Therefore, the ratcheting teeth can be disposed
at an end-face of a gear body that is rotatably mounted on the
output spindle and is rotatively driven with respect to the output
spindle by its own gearing at a speed different from that of the
output spindle or from that of the reaction gear containing the
other set of ratchet teeth.
FIG. 7 illustrates such an arrangement in which the ratchet teeth
25 are formed on an end-face of the wheel 42 of gear 40. The wheel
42 is placed idly on the shaft 19 so that wheel 42 can rotate
relative to the shaft 19. The wheel 42 is held however axially by a
shoulder 43 formed on the shaft 19. The wheel 42 is independently
driven by a gear 42 of the shaft 16 and the percussion frequency is
completely independent of the speed of the output spindle shaft 19
and therefore remains constant upon varying the reduction ratio of
the gear coupling 17-18. The wheel 42 includes the ratchet teeth 25
and is axially fixed on the output spindle 19. The ratchet teeth 25
react on a complementary set of ratchet teeth 24 formed on a
revolving gear body 8 of considerable mass, according to the
principles discussed above whereby the rotating mass 8 contributes
to alternating vibrations transmitted to the gear case and operator
of the tool as well as provides an assist to output spindle in its
rotation into the workpiece.
* * * * *